I. Field of the Invention
The present invention relates to a device suitable for use in performing assays, for example immunological and related assays.
II. Related Art
Assays, for example on biological samples, may be binding assays, for example sandwich or competitive binding assays. Binding assays may make use of immunological interactions. Such assays are known as immunoassays and make use of the high specificity and high affinity of the interaction between an antibody or other immunoglobulin-type molecule and its target antigen.
Binding assays, for example immunoassays, may be useful in medical diagnoses. Diagnostic tests using such assays may be carried out in a laboratory, medical practitioner's surgery or hospital or in a home setting, either by the patient or by a visiting medical practitioner. Devices suitable for carrying out diagnostic tests, particularly those intended for use by non-medically trained personnel, for example patients, may be designed to give a visible test result. These may comprise a support, for example of nitrocellulose, on which an interaction may take place in order to provide the visible test result. Other devices suitable for carrying out diagnostic tests may comprise a capillary test chamber formed between a plastic moulding and a microscope glass slide. These may require a microscope or other instrument in order to determine the test result.
Assays may make use of a lateral flow protocol, for example in which a bibulous or non-bibulous material conducts liquid from one portion of the device to another. Examples of diagnostic test devices using assays, particularly those making use of a lateral flow protocol, are described and reviewed, for example, in U.S. Pat. No. 5,770,460 and in U.S. Pat. No. 4,943,522. As set out in U.S. Pat. No. 4,943,522, a bibulous material may be capable of adsorbing or “imbibing” one or more dissolved or dispersed components of a liquid sample, whereas a non-bibulous material may not so adsorb such components, such that all dissolved or dispersed components of the liquid are carried at substantially equal rates and with relatively unimpaired flow laterally through the membrane. Examples of bibulous materials may include untreated paper, nitrocellulose or nylon and other materials that may be used in chromatographic separation techniques.
The apparatus disclosed in U.S. Pat. No. 4,943,522 comprises a non-bibulous lateral flow membrane which has on its surface a sample application zone and at a lateral distance from the application zone, at least one indicator zone. The membrane may be bound between two sheets.
A further example of an apparatus suitable for performing immunoassays is described in U.S. Pat. No. 4,883,760. This makes use of capillary tubes and a flexible support that enables the end of the capillary tube to be brought into contact with an absorbent material by the application of moderate manual pressure on the support. However, such an apparatus is bulky and suitable only for producing a test result which is assessed by eye.
Known test devices, for example as summarised in the documents cited above, may have disadvantages in terms of convenience or of flexibility or accuracy in performing complex assays. Thus, there is a need for a compact device that allows complex assays, for example those requiring timed incubation or washing steps, to be performed reproducibly. It is an object of the invention to provide an improved assay device.